The following are diamond sizes with corresponding mm sizes. Be very aware that the following millimeter sizes are based on 60% depth with normal girdles and angles. This of course would be completely inaccurate if the diamond in question varied outside of those parameters.
| Approximate Carat Weight | Common Trade Jargon | Millimeter Size |
| 0.005 | half-pointer | 1.00 mm |
| 0.01 | one-pointer | 1.30 mm |
| 0.02 | two-pointer | 1.70 mm |
| 0.03 | three-pointer | 2.00 mm |
| 0.04 | four-pointer | 2.20 mm |
| 0.05 | five-pointer | 2.40 mm |
| 0.06 | six-pointer | 2.60 mm |
| 0.07 | seven-pointer | 2.70 mm |
| 0.08 | eight-pointer | 2.80 mm |
| 0.09 | nine-pointer | 2.90 mm |
| 0.10 | ten-pointer | 3.00 mm |
| 0.11 | eleven-pointer | 3.10 mm |
| 0.12 | twelve-pointer | 3.20 mm |
| 0.13 | thirteen-pointer | 3.28 mm |
| 0.14 | fourteen-pointer | 3.37 mm |
| 0.15 | fifteen-pointer | 3.45 mm |
| 0.16 | sixteen-pointer | 3.53 |
| 0.17 | seventeen-pointer | 3.60 mm |
| 0.20 | twenty-pointer, fifth | 3.80 mm |
| 0.25 | twenty-five-pointer, quarter, one-grainer | 4.10 mm |
| 0.33 | thirty-three-pointer, third | 4.50 mm |
| 0.38 | thirty-eight-pointer, three-eighths | 4.70 mm |
| 0.42 | forty-two-pointer, three-eighths | 4.86 mm |
| 0.45 | forty-five-pointer, three-eighths | 4.97 mm |
| 0.47 | forty-seven-pointer, light-half | 5.05 mm |
| 0.50 | fifty-pointer, half, two-grainer | 5.15 mm |
| 0.55 | fifty-five-pointer, half, two-grainer | 5.32 mm |
| 0.60 | sixty-pointer, five-eighths | 5.47 mm |
| 0.65 | sixty-five pointer, light three-quarter | 5.62 mm |
| 0.70 | seventy-pointer, three-quarter, three-grainer | 5.76 mm |
| 0.75 | three-quarter, three-grainer | 5.90 mm |
| 0.80 | three-quarter, eighty-pointer | 6.03 mm |
| 0.85 | heavy three-quarter, eighty-five pointer | 6.15 mm |
| 0.90 | light carat, ninety-pointer | 6.27 mm |
| 0.95 | light carat, ninety-five-pointer | 6.38 mm |
| 1.00 | one carat, carater, four grainer | 6.49 mm |
| 1.10 | one carat, carater, four grainer, carat-ten | 6.70 mm |
| 1.15 | carat fifteen | 6.80 mm |
| 1.20 | carat twenty, one and a fith | 6.90 mm |
| 1.25 | carat twenty-five, on and a quarter, five grainer | 6.99 mm |
| 1.30 | carat thirty, one and a third | 7.09 mm |
| 1.35 | carat thirty-five, one and a third carat | 7.17 mm |
| 1.40 | carat fourty | 7.26 mm |
| 1.50 | carat and a half, one-fifty, six grainer | 7.43 mm |
| 1.65 | carat sixty-five | 7.67 mm |
| 1.75 | carat seventy-five, one seventy-five, seven grainer | 7.82 mm |
| 1.90 | carat ninety, one-ninety, light two carat | 8.04 mm |
| 2.00 | two carat, two carater, eight graner | 8.17 mm |
| 2.25 | two and a quarter, two twwnety-five, nine grainer | 8.50 mm |
| 2.50 | two and a half, two fifty, ten grainer | 8.81 mm |
| 2.75 | two seventy-five, two and three quarters | 9.09 mm |
| 3.00 | three carat, three carater | 9.36 mm |